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bug(aria/combobox): keys pressed back to back are lost; only the last one reaches the popup

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@drakeo338 已經在處理了。

開始於 2026年10月20日。

  • #33975 來自 @drakeo338 —— 未關閉

評估

難度
2/5
預估耗時
1-3 小時
新手友好度
78/100
Issue 類型
缺陷
描述清晰度
描述清楚
活躍度
活躍
技術堆疊
angular, typescript
領域
accessibility, frontend

研究方向

從 Angular 的 ARIA combobox 實作中的 ComboboxPattern 著手。issue 指出，keyboardEventRelay 在此處被設定，之後會重新分派至 popup control target。追蹤按鍵處理常式和 relay effect，接著為多個連續的 ArrowDown 事件新增或更新單元測試。完成條件是每個事件都依序處理，按三次會移動三個選項。

由索引模型根據 Issue 內容生成。

描述

area: aria/combobox gemini-triaged
Is this a regression?
  • Yes, this behavior used to work in the previous version
The previous version in which this bug was not present was

No response

Description

While the popup is open, ComboboxPattern relays navigation and typeahead keys to the popup through a signal: the key handler does this.keyboardEventRelay.set(e), and an effect later re-dispatches the event on the popup's control target. If a second key arrives before the effect runs, the signal is overwritten and the first key is never relayed.

Effects:

  • Down, Down, Down pressed quickly moves the active option once.
  • Typeahead loses characters: with options item, item-2, item-3, typing item-3 with no delay between keys lands on item; with 60 ms between keys it lands on item-3.
  • Test automation and tools that send keys in a burst (and some assistive technology input) see wrong results. Seen in Chromium through Playwright, and in unit tests.

Related: #33361 (same relay signal, different symptom: a stale event replayed on reopen).

Reproduction
import { Component } from '@angular/core';
import { TestBed } from '@angular/core/testing';
import { Combobox, ComboboxPopup, ComboboxWidget } from '@angular/aria/combobox';
import { Listbox, Option } from '@angular/aria/listbox';

@Component({
  imports: [Combobox, ComboboxPopup, ComboboxWidget, Listbox, Option],
  template: `
    <div ngCombobox #combobox="ngCombobox" tabindex="0">Pick one</div>
    <ng-template ngComboboxPopup [combobox]="combobox">
      <div ngListbox ngComboboxWidget #listbox="ngListbox" focusMode="activedescendant"
        [activeDescendant]="listbox.activeDescendant()">
        @for (o of options; track o) {
          <div ngOption [value]="o" [label]="o">{{ o }}</div>
        }
      </div>
    </ng-template>
  `,
})
class Repro {
  options = ['alpha', 'bravo', 'charlie', 'delta'];
}

const key = (el: Element, k: string) =>
  el.dispatchEvent(new KeyboardEvent('keydown', { key: k, bubbles: true }));

it('handles each key pressed back to back', async () => {
  const fixture = TestBed.createComponent(Repro);
  await fixture.whenStable();
  const combobox = fixture.nativeElement.querySelector('[ngCombobox]');
  combobox.focus();
  key(combobox, 'ArrowDown');            // open
  await fixture.whenStable();
  key(combobox, 'Home');
  await fixture.whenStable();
  key(combobox, 'ArrowDown');
  key(combobox, 'ArrowDown');
  key(combobox, 'ArrowDown');
  await fixture.whenStable();
  const id = combobox.getAttribute('aria-activedescendant');
  expect(fixture.nativeElement.querySelector(`[id="${id}"]`).textContent.trim())
    .toBe('delta');                       // actual: 'bravo'
});
Expected Behavior

Each key event is handled, in order. Three Down presses move three options.

Actual Behavior

Only the last key since the effect last ran is relayed. Three Down presses move one option ("bravo" in place of "delta").

A possible fix: relay each event synchronously from the key handler (or queue them), not through a single-value signal.

Environment
  • Angular: 22.2.1
  • CDK/Material: @angular/cdk 22.2.3, @angular/aria 22.2.3 (also in 22.3.0-next.2 and main)
  • Browser(s): Chromium (Playwright); Vitest with happy-dom
  • Operating System (e.g. Windows, macOS, Ubuntu): macOS
主要語言
TypeScript
星號
25k
分支
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平均合併
1 天 5 小時
30 天內合併 PR
67

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